Feeding our pets is one of the most important things we do as pet owners. There is an abundance of options to choose from when it comes to feeding our cats. So understanding the nutritional requirements of our pet cats is important to ensure we can make an informed choice. One particularly essential component of a cat’s diet is Vitamin A. 

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What is Vitamin A?

Vitamin A is a fat-soluble vitamin that can be found in many different types of foodstuffs. Cats do not produce their own vitamin A, so it is important that they consume the right amount in their diet.

Vitamin A is an essential nutrient in cats and important for many bodily functions including:

  • Eye health, including night vision – Vitamin A is a component of proteins that are important for vision.
  • Skin health – Vitamin A is involved in the creation of the cells within the skin.
  • Cell growth, allowing the growth and development of organs and other soft tissue structures in growing animals, and the repair of injuries.
  • Immune function – Vitamin A helps the body deal with potential infections by providing mechanical defences with its role in skin and organ health, including production and secretion of mucous, and by assisting with the development of cells, such as white blood cells, which are essential in allowing the body to deal with infection. 

Vitamin A is the collective name given to a group of chemical compounds which include retinol, retinal esters and carotenoids such as beta-carotene. Some of these chemical compounds can be used by the body as vitamin A as soon as they are ingested such as retinol, others can be used by the body to make a usable form of vitamin A, these are known as provitamin A compounds. 

It is important to note that all animals are different and not all of these compounds can be converted to a useble form of vitamin A in all species, as this process of conversion requires the body to have specific enzymes in order to do this. This is important because if an animal is fed a compound which it cannot use, it will still be deficient in that vitamin despite it being in its diet. The ability of the animal’s body to use the compound is vitally important. 

The type of Vitamin A is important to cats

As mentioned above, several chemical compounds can be named as vitamin A, but not all of them will be able to be used as vitamin A straight away when they are ingested. Some chemicals, known as provitamin A compounds, will need to be converted by the body into a usable form of the vitamin. Cats are unable to use provitamin A compounds which need to be converted before they are used, as they lack the enzymes required to do this. This means if they are fed these compounds they will still be deficient in vitamin A. Instead, cats require what is known as a preformed type of vitamin A in their diets. Preformed means the vitamin is already in its usable state in the foodstuff, and when ingested by the cat, can be used as vitamin A by the body straight away. 

Provitamin A compounds include carotenoids such as beta-carotene, which is a compound derived from plant matter. This cannot be used as a source of vitamin A in cats. 

Preformed vitamin A includes retinol found in animal sources. Retinol is the usable form of vitamin A, so when ingested the body can use it as vitamin A without the need for conversion. 

When looking at the composition of the food you are feeding your cat it is therefore important to make sure the vitamin A in the foodstuff is retinol, and not a provitamin A compound such as beta-carotene. 

What happens if cats have too little vitamin A?

Hypovitaminosis A is the technical term given to the condition which occurs when an animal is deficient in vitamin A. 

In cats, deficiency in vitamin A can result in a number of symptoms which include:

  • inability to see in the dark or difficulty orienting themselves at night (night blindness)
  • dryness of the membranes around the eye (the conjunctiva)
  • reduced interest in food or not eating (anorexia)
  • weight loss 
  • changes to the skin and coat/fur quality 
  • poor immune function and increased susceptibility to infections 
  • inflammation of the kidneys (nephritis)
  • reproductive issues including stillbirths and congenital defects in offspring 
  • skeletal issues such as overgrowth of bones

As you can see from the list of symptoms above, having too little vitamin A can have severe consequences for cats and lead to a number of harmful health conditions. 

Is it possible to have too much vitamin A?

Yes, it is possible to have too much vitamin A.

Vitamin A is a fat-soluble vitamin which means it is absorbed and transported by fatty tissues within the body. It is stored mostly within the liver and fatty tissues. When supplies are low, the body can mobilise this store of vitamin A for use in its essential functions. 

Being a fat-soluble vitamin, it is not able to be excreted by the body easily. In comparison, water soluble vitamins are able to be easily excreted as the body gets rid of waste water, and are not stored in the body, so are therefore unlikely to build up to toxic levels. 

Having a store of vitamin A is normally a benefit to the animal, however if too much vitamin A is ingested, then excessive stores will build up in the body which can lead to toxicity, known as hypervitaminosis A. 

In cats, excess vitamin A can cause a number of symptoms which include:

  • degeneration of the bones – especially in the neck (cervical spondylosis) and spine
  • tooth loss
  • stunted or slow growth 
  • reduced interest in food or not eating (anorexia)
  • weight loss
  • bone fractures 
  • internal bleeding (haemorrhage)
  • congenital abnormalities including cleft palate, shortened mandible and an enlarged heart 
  • liver damage

What food sources are high in vitamin A?

Animal products including liver, fish oils and dairy products are all considered good sources of dietary vitamin A. Plant products contain provitamin A sources known as carotenoids, which as previously discussed are not a suitable source of vitamin A for cats. 

It is important to remember that most commercially available cat foods will be nutritionally balanced, and contain the appropriate amount of vitamin A that your cat needs, so supplementation with additional food sources is not necessary, and should be avoided to prevent toxicity. If you are concerned about the amount of vitamin A in your pets diet and want to check they are receiving the appropriate amount and type of vitamin A, then you can consult with your veterinary surgeon who should be able to assist you with this. 

You can read more about vitamin A and other essential minerals and vitamins in the online Small Animal Clinical Nutrition (5th Edition) Chapter 6 

Summary:

  • Vitamin A is an essential vitamin in your pet cat’s diet.
  • Vitamin A is a fat soluble vitamin which is commonly stored in the liver and in fatty tissue.
  • Deficiencies, known as hypovitaminosis A, and toxicities, known as hypervitaminosis A, can occur if too little or too much vitamin A is absorbed by your pet.
  • Vitamin A is important for many aspects of your cats health including vision, skin condition and immune function.
  • Cats need preformed vitamin A from animal sources, unlike other species they cannot metabolise plant based provitamin A sources and will become deficient in vitamin A if only fed these sources.

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